Detailed sections of the esophagus
- Cervical esophagus: runs posterior to the trachea for 4-5cm before ending at the level of the thoracic inlet. This segment borders the carotid sheath, recurrent laryngeal nerve, and thyroid gland bilateralyl as well as teh thoracic duct to the left. Posteriorly, the cervical esophagus rests on the vertebral column.
- Thoracic esophagus: spans from the thoracic inlet to the EGJ at the level of T11. This segment is subdivided into the upper thoracic, midthoracic, and lower thoracic regions. The border between the upper and mid-thoracic esophagus is at the level of the tracheal bifurcation. The mid-thoracic esophagus continues to the level of the inferior pulmonary veins, where it becomes the lower thoracic esophagus.
- Abdominal esophagus: a short segment of the esophagus below the esophageal hiatus which overlaps with the lower thoracic esophagus. The abdominal esophagus is primarily retroperitoneal, although a small portion is covered by peritoneum/serosa. Inside the abdomen, the esophagus passes behind the left lobe of the liver.
Lymph nodes: For lymph node stations for staging and management of esophageal cancer, refer to this publication by Wang et al. 2018 detailing the anatomy of the lymph nodes: https://doi.org/10.2147/CMAR.S182436 .
Histological layers of the esophagus
- Mucosa: consists of stratified squamous epithelium, lamina propria, and muscularis mucosa. The squamocolumnar junction (Z-line) separates the stratified squamous epithelium of the esophagus and simple columnar epithelium of the stomach. Normally the Z-line coincides with the EGJ, however, in Barrett’s esophagus, metaplasia causes the squamocolumnar junction to migrate proximally.
- Muscularis propria: the upper third of the esophagus is striated muscle while the lower third is smooth muscle. A mixture of both striated and smooth muscle can be found in the middle third of the esophagus.
- Adventitia: thin and with small amount of peritoneal (serosal) covering of the abdominal esophagus. The esophagus’s thin adventitia and lack of serosa facilitate the locoregional progression of esophageal cancer.